用DLL实现插件的简单演示

这是DLL的代码



library MyDll;



uses

  SysUtils,

  Dialogs,

  Classes;



procedure ShowInfo(info:PChar);stdcall;

begin

  ShowMessage('您选择了【'+info+'】');

end;



function GetCaption:Pchar;

begin

  Result := '中国';

end;



exports ShowInfo,        

        GetCaption;



{$R *.res}



begin

end.

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这是调用窗体的代码

本例只使用了一个DLL，所以当有多个DLL时，需要循环DLL所在目录，依次加载DLL



unit Main;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls, Menus, ExtCtrls;



type

  TShowInfo = procedure (info:PChar);stdcall;

  TGetCaption = function : PChar;stdcall;





  TForm1 = class(TForm)

    Button1: TButton;

    Button2: TButton;

    MainMenu1: TMainMenu;

    Image1: TImage;

    procedure Button2Click(Sender: TObject);  private

    { Private declarations }

    FHandel : THandle;     //DLL句柄

    FProAddress: Pointer;  //DLL中ShowInfo的地址

    showinfo: TShowInfo;   //为动态加载DLL而设

    procedure LoadPlusIn;  //加载插件（DLL）

    procedure ItemClick(Sender: TObject);   //自定义菜单点击事件

  public

    { Public declarations }

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



procedure TForm1.Button2Click(Sender: TObject);

begin

  LoadPlusIn;

end;



procedure TForm1.ItemClick(Sender: TObject);

begin

  @showinfo := FProAddress;     //取地址

  if @showinfo <> nil then

    showinfo(PWideChar(TMenuItem(Sender).Caption));  //执行DLL中的ShowInfo

end;



procedure TForm1.LoadPlusIn;

var

  getcaption: TGetCaption;

  item : TMenuItem;

begin

  FHandel := LoadLibrary('MyDll.dll');   //加载

  if FHandel = 0 then

  begin

    ShowMessage('加载失败！');

    Exit;

  end

  else

  begin

    @getcaption := GetProcAddress(FHandel,'GetCaption');    //取DLL中GetCaption地址

    if @getcaption <> nil then

    begin

      item := TMenuItem.Create(MainMenu1);    //创建一个菜单

      item.Caption := getcaption;             //取Caption，即调用DLL中的GetCaption

      FProAddress := GetProcAddress(FHandel,'ShowInfo');  //取得DLL中ShowInfo的地址

      item.OnClick := ItemClick;              //赋予菜单项的点击事件

      MainMenu1.Items.Add(item);              //添加到主菜单

    end;



  end;

end;



end.

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